A control device of a steering device such as a power steering device serves to selectively control two controls: an assist control which controls an actuator including a motor or the like based on a driving state of a vehicle to provide a steering assist force for assisting a steering force of a driver and an automatic steering control which generates a target steering angle based on an instruction value of a host controller and controls the actuator to automatically adjust a steering angle of a steered wheel (for example, refer to JP H4-55168 A: PTL 1).
Further, to minimize a state in which the steering assist function of the steering device is lost during running, a steering device including two systems configuring an electric motor drive device which are composed of a combination of a drive device including an inverter or the like and a pair of electric motor windings corresponding to the drive device are used (for example, refer to JP 2012-25374 A: PTL 2). In this steering device, when a fault of the inverter or the winding set of any of the two systems is detected, a power supply relay of the fault system is shut off, and an upper limit value (maximum current limit value) of a current supply limit value of the normal system is set to be the same value as before the fault detection. Further, when a vehicle speed is less than a predetermined threshold value, the maximum current limit value is set to be zero to prevent a steering assist torque from being generated.